Unable to delete a subnet I created in GCP

Assuming the VMs have been deleted the only way is to use command line to delete the Internal Reserved IP addresses.

Open Cloud Shell and connect it to the correct project then run the highlighted commands:

user123@cloudshell:~ (cellular-project-258333)$ gcloud compute addresses list
NAME          ADDRESS/RANGE  TYPE      PURPOSE       NETWORK  REGION       SUBNET      STATUS
k8s-worker-1  10.175.0.4     INTERNAL  GCE_ENDPOINT           us-central1  k8s-subnet  RESERVED
k8s-worker-2  10.175.0.5     INTERNAL  GCE_ENDPOINT           us-central1  k8s-subnet  RESERVED
k8s-worker-3  10.175.0.6     INTERNAL  GCE_ENDPOINT           us-central1  k8s-subnet  RESERVED


user123@cloudshell:~ (cellular-project-258333)$cloud compute addresses delete k8s-worker-1 k8s-worker-2 k8s-worker-3 --region us-central1                                                      
The following addresses will be deleted:
 - [k8s-worker-1] in [us-central1]
 - [k8s-worker-2] in [us-central1]
 - [k8s-worker-3] in [us-central1]

Do you want to continue (Y/n)?  Y

Deleted [https://www.googleapis.com/compute/v1/projects/cellular-project-258333/regions/us-central1/addresses/k8s-worker-1].
Deleted [https://www.googleapis.com/compute/v1/projects/cellular-project-258333/regions/us-central1/addresses/k8s-worker-2].
Deleted [https://www.googleapis.com/compute/v1/projects/cellular-project-258333/regions/us-central1/addresses/k8s-worker-3].

Now the network resources such as subnets and VPCs can be deleted.